Can't answer that for you. I've used Tiles many times on various project, but I am certainly no expert on it. In my experience with it, I turn to the logs for help when I have these kinds of errors.
Or, if that doesn't help, step 2 (for me) is to remove the entire contents of that particular tile, and slowly replace it piece by piece until it stops rendering, then examine the part you just put back. I know that sounds crazy, but it works for me.....and it almost always ends with "(head smack)...what was I thinking?".
It's not really Tiles' fault; remember that those errors are being thrown essentially by JSP include operations, at which time there's no ability to redirect to an error page (because the response is already committed.) What would you have Tiles do? Dump the error to the page? That may work for some users, but not all, and not all errors can be handled that way anyway.
So far, the best results I've had for something like this is with the JSTL core <c:catch> tag, and a homegrown tag I have which takes an Exception class and can be configured to show or not show the exception's message and which can be configured to dump the root-cause stack trace, optionally (usually) enclosed in HTML comments.
With the chain based request processor, the exception propagates all the way to the configured ExceptionHandler, but the base implementation of that class expects to be able to forward to an error page; perhaps a variant could be written which tests to see if the response is committed and takes a different route. I've experimented with some things around that, but haven't found anything I was so excited about yet.
I definitely agree that troubleshooting runtime exceptions from JSPs is frustrating, which to me is just another reason to design your app so that everything except the most basic happens before control is dispatched to the view.
Joe
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Joe Germuska [EMAIL PROTECTED] http://blog.germuska.com "Narrow minds are weapons made for mass destruction" -The Ex
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